Chemical and/or biological deposition in industrial process fluid adversely affects processing efficiency and can force operational downtime or even plant shutdown. It is well known in the art that mineral and/or biofilm deposition in cooling towers, heat exchangers, or other fluid processing vessels reduces critical heat transfer efficiency, decreases flow velocity, and can lead to structure fatigue and crack formation. Moreover, the maintenance of service water heat exchanger performance is a safety issue for utility plants, especially nuclear power plants. Quite obviously then, there is a need to provide for the accurate and timely detection and measurement of chemical and/or biological deposit accumulation in industrial process fluid and processing vessels.
Traditionally, the onset of deposition in industrial process fluid has been monitored by measuring either the temperature difference across a heat transfer surface or by measuring physical and chemical changes caused by deposition on a clean surface immersed in the fluid by way of electrochemical, optical, spectroscopic, or acoustic methods. Several monitoring systems based on temperature measurement have been used to monitor mineral and biofilm deposition, especially in cooling towers and heat exchangers. The heat transfer surface in many of these systems is simulated by electric heat. These systems are usually easy to set up and operate. They provide heat transfer resistance values for the simulated heat transfer surface, which can be correlated to the overall heat transfer efficiency of heat exchangers. However, deposit monitoring based on temperature measurement is subject to process variations such as changes in process temperature, flow velocity, and environmental temperature. Additionally changes in power supply to the electric heater in a side stream heat flux simulator can cause similar errors. This is why commercially available deposit monitoring systems lack the sensitivity required to detect the early onset of deposit accumulation. Consequently, detecting the early onset of deposit accumulation in a cost effective manner has been heretofore difficult to achieve.
Methods used to measure the physical and chemical changes caused by deposition include optical transmittance, fluorescence, and quartz crystal microbalance. The sensitivity of these methods is usually high. However, these methods require relatively expensive instruments. Variations and process parameters affect the measurements, and a heat transfer surface may not be easily incorporated.
The foregoing has outlined a need for an improved system for the monitoring and measurement of deposit accumulation in industrial process fluids and fluid transport vessels. It is therefore desirable to have a fast, accurate, and cost-effective system that is capable of detecting and measuring the early onset of chemical and/or biological deposition.